Introduction

Each molecule makes four hydrogen bonds with its four nearest neighbors, two as a hydrogen bond donor and two as an acceptor.

All the possible proton arrangements in the ice strucrure are not energetically equivalent and we sample and weight them with a Monte Carlo approach. For this purpose, a specific algorithm was created (see: 10.1063/1.1568337), that allows to employ special proton reordering moves, which lead to an effective sampling of the ice dipole (N.B: different proton arrangement = different dipole).

The dielectric constant of a system describes its response to an external electric field.
If the dipole moment is properly sampled, one can compute the dielectric constant of ice, by applying the Kubo Formula. This is valid in the approximation that the response of the system to the time-dependent perturbation (the field) is linear.

Task 2: Gather more samplings

You can gather more samples by launching multiple independent runs in parallel with different random number seeds. The seed is given by the RND_DETERMINISTIC keyword. The gathered trajectories can then be analyzed collectively with the python-script:

Topology File

This file specifies the topology of the system (which atoms, bonds, angles in the water molecule). It allows the program to distinguish which atoms belong to which water molecule, and therefore discriminate between inter and intramolecular interactions.